The commercial aircraft manufacturers have requirements for food storage that require equipment for storing food be capable of achieving and maintaining temperatures that will preserve perishable food stuffs for consumption by passengers during flight. A food storage structure such as a galley must have a level of thermal insulation that resists conductive losses to allow the galley to meet or exceed the manufacturer's and airworthiness authority's requirements for the safe storage of food. The minimum thermal resistance level of a food storage structure is usually specified as an average value for the entire monument, which takes into account losses through cold bridges between the chilled compartments and the warmer exterior ambient temperatures. These cold bridges can take the form of metallic items such as floor fittings, edge members, potted inserts, bobbins, embedded and mouse hole blocks, sliding tables, door hinges, latches, and access panels, as well as poorly insulated non metallic areas such as recessed panels, cut outs and cable passes.
The average thermal resistance performance of a chilled storage structure therefore equates to the capability of the non metallic panel, less any losses through cold bridges and poorly insulated areas. By test, it has been established that a 13 mm (roughly ½″) Nomex cored pre-preg structural panel is insufficient to maintain galley chilled compartments at or below the required safe temperature for perishable food stuffs. In order to improve the monuments thermal capability, either the thickness of the panel has to be increased or secondary insulation has to be added to the structure.
In addition, the reduction of intrusive noise into an aircraft cabin, usually produced by the routine operation of an in-flight airline catering service, is a prime objective of the aircraft manufacturers. Most of this noise is produced by Galley Insert Equipment (GAINS), e.g. ovens, refrigerators, beverage makers, trash compactors, blenders, etc., and by the cabin crew preparing meals, e.g., removing standard meal boxes from their compartments, filling meal carriers for ovens, slamming compartment doors, removing carts from their compartments, and the like. Because this noise is bothersome to the passengers, the aircraft manufacturers seek to reduce the overall noise in the passenger cabin by providing sound absorbers. This comes at the expense of weight and cost, which are constant factors in an aircraft design and operation.